The first superhero ever is often credited to Superman, who made his first appearance in Action Comics #1 in 1938. Created by Jerry Siegel and Joe Shuster, Superman's debut marked the beginning of the superhero genre in comics.
However, there were some earlier characters who had some elements of what we consider superheroes today, such as The Shadow, Zorro, and The Phantom.
But Superman is generally considered the first true superhero due to his immense popularity and defining characteristics, such as super strength, speed, flight, and invulnerability.